At the end of the morning session at the Circuit de Catalunya, where every team on the grid circulated, Jenson Button was clearly the fastest runner at the wheel of the Mercedes-powered BGP001.

Following months of uncertainty and engine silence, the team formerly known as Honda made a loud statement on Monday as the final group test of the 2009 pre-season began.

At the end of the morning session at the Circuit de Catalunya, where every team on the grid circulated, Jenson Button was clearly the fastest runner at the wheel of the Mercedes-powered BGP001.

The significant of test times is often overstated, but the Brackley based team - now renamed Brawn GP following a buyout - has always been bullish about its hopes for 2009 as the foundations of the car took place at the factory prior to Honda's decision to quit the sport.

Part of the reason for the impressive pace could simply be the switch to Mercedes-Benz power, with last year's Honda believed to have boasted up to 60 horsepower less.

Despite this being Brawn's first test since the Honda pullout, Button's best lap, after 30 tours of the Spanish layout, was quicker than his fastest lap of the grand prix at the same circuit last year.

Moreover, he was nearly seven tenths faster than the next quickest car, Jarno Trulli's impressive Toyota. The new Toro Rosso was fifth fastest and immediately on the pace of the sister Red Bull.